The most common type of hand-actuated brake assembly used with bicycles today is the caliper-type brake assembly. The present invention relates to a new design for such a type of bicycle brake. Such brake assemblies usually include a pair of arms pivotally mounted to a bicycle frame, and actuated by a cable connected to a hand lever. The arms are usually pivotally mounted on opposite sides of the front wheel and/or the back wheel. One end of each arm is generally located near the rim of each wheel and includes means for mounting a friction braking pad generally made of rubber or some similar material. The friction braking pads are each attached to the arms so as to be opposite the wheel rim.
Brakes of this type are actuated by a cable connecting the brake arms to a hand-actuated lever attached to the bicycle handle bars. The hand lever, when pulled on by the rider, applies a pulling force to the cable. The brake cable is contained within a sleeve anchored to the bicycle frame. As the cable moves in response to the motion of the hand lever, it pulls on one or both brake arms, causing them to pivot about their points of attachment. As the brake arms pivot, the friction braking pads are caused to come into contact with the wheel rim, causing the bicycle to slow due to the friction between the wheel and the friction braking pads. When the force is released from the hand lever, the cable relaxes, thereby allowing the arms of the brake assembly to reverse the direction of pivoting about their attachment points, moving the friction braking pads out of contact with the wheel rim. When the brakes are not in use, the action of one or more springs usually maintains the brake arms in an open position with the friction braking pads out of contact with the wheel rim.
Many variations on caliper-type bicycle brake assembly exist. These variations include the side-pull brake, the center-pull brake, and the cantilever-type brake. In a side-pull brake assembly, the arms of the brake assembly are pivotally mounted at a single point of attachment to the frame of the bicycle. The attachment point is generally on the top of the fork at the point where it divides into two branches between which the wheel is inserted and at the end of which the wheel is mounted.
In a cantilever-type brake assembly, the brake arms are usually attached on opposite extensions of the fork of the bicycle frame. The brake actuating cable from the hand lever usually splits into two branches at a point near the bicycle brake assembly, one of the branches being attached to one brake arm lever and the other cable attaches to the other brake arm lever. Force is applied to the cable via the hand lever, causing the brake arm levers to rotate about their points of attachment, thereby causing the friction braking pads to engage the wheel rim. Such a cantilever-type brake assembly results in a more direct and even application of power to each of the brake arms, unlike the side pull brake which depends upon a spring action for indirect application of force to the brake arm which does not have an extension to which the brake cable is attached.
In the prior art known bicycle brake assemblies discussed above, the braking power applied to the brake arm levers and consequently to the friction braking pads on the wheel rim is directly proportional to the amount of force applied to the brake cable by pulling on the hand brake lever. The more force that is applied to the brake lever, the further the cable will travel and thus more force will be applied by the friction braking pad to the wheel rim. If the rider of the bicycle wishes to stop faster or needs to apply more force in an emergency situation, he or she must simply continue to apply more and more force to the hand lever and actuating cable to achieve greater braking power. None of the known type of bicycle brake assemblies provide for any mechanical advantage in braking power other than by applying increased force to the hand-operated braking lever.
This failure to deliver adequate braking power is especially noticeable on wheel rims made of plastic. Further, the problem particularly manifests itself on "BMX" type bicycles, which not only have plastic wheel rims, but also usually only have one brake assembly. "BMX" bicycles are often used to perform stunts which frequently involve sharp, precise, and very quick stops after which the rider may pivot the bicycle on one wheel or perform another acrobatic movement with the bicycle. Such stunt movements are made quite difficult by the inability of the bicycle brake to make these pinpoint stops. In part, due to the smoothness of plastic wheel rims, the interaction between the friction braking pads and the wheel rim(s) failed to provide the braking capability necessary to allow the rider to accomplish the desired movements. The present invention succeeds where known bicycle brakes fail by providing the ability to greatly magnify the force imparted by the rider to the brake cable.